The present invention is directed to a rotary printing machine which is equipped with an interchangeable cylinder, especially a screen ink transfer cylinder, which is also called "anilox" cylinder and is held between two side walls of the machine frame by a freely disengageable holding and driving means.
With a view to optimize the use of the rotary printing machine, exchangeable anilox or transfer cylinders have become a more desirable feature.
In fact, depending on the given print motif, for example a very intensive solid requiring considerable ink quantities or a fine meshed screen necessitating much less ink, it is possible to vary the quantity of ink being transferred by either varying the viscosity of the ink by dilution or to exchange the anilox or transfer cylinder of which the volume of the bits on the cylinder surface will determine the quantity of ink being transferred. Considering the difficulties to master the ink homogeneity and viscosity, an increasingly preferable solution consists in exchanging the anilox or transfer cylinders.
Patent Documents FR 2 503 628; WO-87/04665 and EP-315 917 present rotary printing machines equipped with one or several cylinders and the driving means lodged in a so-called cassette. The cassette can be removed horizontally from the machine perpendicularly to the lateral or side wall of the machine. As may be gathered, the weight of the exchangeable assembly of the cassette comprises the weight of the cylinders to be exchanged must also include the weight of the cassette body, as well as the cylinder holding and driving means, which are attached thereto. Handling of such an assembly will, thus, be so difficult that the exchange will not be carried out as often as it should.
U.S. Pat. No. 4,901,641, whose disclosure is incorporated herein by reference thereto, discloses a rotary printing machine. In this Patent, a printing cylinder is held by two axles which have tapered or frusto-conical ends which extend into equally tapered apertures arranged coaxially on both lateral ends of the cylinder. The axle may be freely advanced or retracted, as required, toward and from the cylinder in order to seize the cylinder or to disengage it. Moreover, an ink basin is kept underneath the printing cylinder by a bracket arrangement, which can be rotated around a vertical threaded shaft and also descend along the threaded shaft. The linkage between the basin and the bracket is also rotatably movable. The inner surface of the basin is provided with a V-shaped, half-rigid support for the cylinder.
With the bracket rising, the basin will come into contact with the lower surface of a cylinder and, thus, support its weight. The cylinder holding axles will then be retracted to release the cylinder and, by a double rotation of the basin with regard to the bracket as well as the bracket with regard to the threaded shaft, it will be possible to disengage the printing cylinder through an upstream side of the printing device and then across one of the side walls. It becomes obvious that the bracket holding the cylinder at the very end of the basin and the cylinder should be particularly well-dimensioned and that the movement to be carried out for the release of the cylinder is rather complex for less qualified workers.